"Unknown task" error in Celery Flower when posting a new task

Question

I'm running celery 3.1.11 and flower 0.6.0 .

I have a celery application configured as such;

# myapp.tasks.celery.py
from __future__ import absolute_import    

from celery import Celery


class Config(object):
    BROKER_URL = 'amqp://'
    CELERY_RESULT_BACKEND = 'amqp'

    CELERY_TASK_RESULT_EXPIRES = None
    CELERY_RESULT_SERIALIZER = 'json'
    CELERY_INCLUDE = [
        'myapp.tasks.source',
        'myapp.tasks.page',
        'myapp.tasks.diffusion',
        'myapp.tasks.place',
    ]
)

celery = Celery('myapp')
celery.config_from_object(Config)    


if __name__ == '__main__':
    celery.start()

I execute the celery worker using the following command:

$ celery -A myapp.tasks worker --loglevel=INFO -E -Q celery

I can see the complete list of available tasks in the worker output.

[tasks]
  ...    
  . myapp.tasks.diffusion.post_activity
  ...

I then execute the flower server with the following command:

$ celery -A myapp.tasks flower

Now, whenever I try to post a new task via the Flower REST API, I get a 404 error with an error message "Unknown task TASK_NAME".

[W 140423 12:16:17 web:1302] 404 POST /api/task/async-apply/myapp.tasks.diffusion.post_activity (82.225.61.194): Unknown task 'myapp.tasks.diffusion.post_activity'
[W 140423 12:16:17 web:1728] 404 POST /api/task/async-apply/myapp.tasks.diffusion.post_activity (82.225.61.194) 4.68ms

I've put a pdb breakpoint in the flower API handler, and it appears that the only tasks available when the requests is handled are the following:

ipdb> pp celery.tasks
{'celery.backend_cleanup': <@task: celery.backend_cleanup of yoda.tasks.celery:0x7fb9191eb490>,
 'celery.chain': <@task: celery.chain of yoda.tasks.celery:0x7fb9191eb490>,
 'celery.chord': <@task: celery.chord of yoda.tasks.celery:0x7fb9191eb490>,
 'celery.chord_unlock': <@task: celery.chord_unlock of yoda.tasks.celery:0x7fb9191eb490>,
 'celery.chunks': <@task: celery.chunks of yoda.tasks.celery:0x7fb9191eb490>,
 'celery.group': <@task: celery.group of yoda.tasks.celery:0x7fb9191eb490>,
 'celery.map': <@task: celery.map of yoda.tasks.celery:0x7fb9191eb490>,
 'celery.starmap': <@task: celery.starmap of yoda.tasks.celery:0x7fb9191eb490>}

No tasks seem to be available. However, when I use the task async_apply() method in a shell, the task is executed by the worker.

Any idea what I'm doing wrong? Thank you!

Edit: when I'm using celery 3.0.19 and flower 0.5.0, it works seemelesly.

Answer 1

This error was due to a bug in Flower and now has been resolved:

Issue: https://github.com/mher/flower/issues/200

Resolving commit: https://github.com/mher/flower/commit/bfba1eec90124c92586c480aebaf98ae63c31276

Answer 2

I was experiencing similar problems with flower. My configuration was using redis.

Situation has improved at the moment I have started flower with explicit value for option "broker" (do not ask me why).

In your situation I would try

$ flower -r "amqp://"

Anyway, I would also make sure, that you start celery and redis from an environment, which has proper access to all your libraries.